Coupling effects of two forward-facing triangular bubbles interacting with a planar shock wave

The study presents numerical simulations of two forward-facing equilateral triangular bubbles under the impact of a planar shock wave to study the induced instabilities, vortex formations, and coupling effects. The simulations are performed using a pressure-based compressible two-phase flow solver, integrated with a coupled level set volume of fluid algorithm to capture the interface, and incorporating a high-resolution total variation diminishing scheme to study shock–interfacial interactions. The evolution of the two bubbles is analyzed by varying the initial separation distance, Atwood number (At), and Mach number (M). Qualitative and quantitative analyses are performed to study the interfacial features, i.e., length, height, upstream and downstream locations of the distorted bubbles, the vortex interactions, baroclinic vorticity produced, and coupling jet formation. The results show that the initial separation distance significantly affects the coupling between the bubbles; a smaller distance leads to stronger coupling, which, in turn, promotes vortex interactions and earlier coupled-jet formation. Furthermore, the effects of varying the Atwood number reveal negligible inter-bubble interaction for a positive Atwood number up to 0.67, even for the smallest separation distance of 2 mm. An increase in the Mach number results in rapid interfacial motion, enhanced vortex structures and interactions, and stronger coupling jet formation. The results highlight the roles of geometric configuration, initial separation distance, Atwood number, and Mach number in determining coupling effects, the growth of interfacial instabilities, and vortex formation in Richtmyer–Meshkov instability studies. A scaling law is further established to quantify the coupling metric dependence on different parameters.